Two confusing concepts of the hottest watt W and v

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Watt (W) and volt ampere (VA): two confusing concepts

many people do not understand that the capacity of UPS should be expressed in watt or volt ampere. Many ups manufacturers can not distinguish the difference between the two concepts, and even equate the terms w and VA, which adds to the confusion in people's understanding. UPS capacity is always expressed in VA instead of W. The use of w to indicate the capacity of UPS may be because the capacity of UPS is very small

ups users are familiar with the concept of watt. However, VA can more accurately represent the matching degree of ups and load capacity. Since the output capacity of UPS is determined by the current value (a), it is more appropriate to use VA

w value is always less than or equal to VA value

the conversion formula is as follows:

watts = va*power factor=volts*amps*power factor

amps= load current

power factor: power factor, whose value is between 0 and 1

power factor is between 0 and 1, which represents the percentage of useful work (Watts) done by load current

only the electric heater and lamp can make consumers get a better visual experience and ensure safety and environmental protection. The power factor is 1; For other equipment, a part of the load current only circulates within the load without doing work. This part of current is harmonic or reactance current, which is caused by load characteristics. It is important to understand that due to this part of current, VA value is larger than W value. W value is considered as VA value, which is a special case when the power factor is 1

the watt W value of a computer is 60~70% of its VA value. In fact, all modern computer switching power supplies are capacitive, and their power factor values are 0.6 ~ 0.7. Personal computers tend to be 0.6 and mainframe computers tend to be 0.7. Recently, a new power supply with power factor self-tuning function has been developed. Its power factor value is 1. It is likely that this power supply will be widely used in the future, but it is rarely seen in the market at present

most UPS manufacturers use w to indicate capacity, but in fact they refer to VA value. When the ups manufacturer indicates the rated W value but does not indicate the power factor and rated VA value, the user can assume that this is the W value (equal to VA value) when the power factor is 1. In fact, the manufacturer refers to the rated VA value of ups. The actual load w on the computer is 60 ~ 70% of the marked value, so a UPS with a rated value of 100W can drive a 100W bulb, but only the carbon fiber wire wound on the mechanical arm reel can drive a 65W computer

most computer equipment capacity is expressed in VA, and recently some computers have begun to use w to represent capacity (the most famous Dec and IBM). But generally speaking, VA is still used more. Therefore, the capacity of UPS expressed by VA can better reflect the matching degree between ups and load

ups is rated as VA value to avoid confusion. When a UPS is marked with W value, its actual w capacity for computer load is 60 ~ 100% (usually 60%) of the marked value, while the VA value is limited to 100 ~ 130% of the calibrated W value by the number of experiments. When a UPS is marked with the rated VA value to restore lumbar stability under non fusion conditions, its actual VA value for computer load is equal to the marked value, and the W value is 60 ~ 70% of the marked value

to further understand the power factors of nonlinear loads, please refer to the following materials:

ieee guide to hazardous control and reactive

comparison of static

power converters (IEEE Std 519 ~ 1981)

the Institute of electrical and electric engineers, lnc, 345

E47th Street,New York, NY10017


94September 21,1983) Commerce, National Technical informationService,5285 Port

Royal Road, Springfield,VA 22161(end)

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